Electric field whistle

ABSTRACT

In one embodiment, an electric field sensor is provided including an elongated conductor; a circuit including an input and an output connected across the elongated conductor wherein said circuit includes a DC to AC signal converter; wherein said elongated conductor is operative to impose a DC signal on said circuit input in response to being exposed to an electric field and broadcast an AC signal converted from said DC signal in response to said electric field being greater than a threshold level.

TECHNICAL FIELD

The disclosure relates to electric field sensors and more particularlyto an electric field sensor that is combined with an antenna thatoperates to emit a signal (whistles) at a predetermined frequency inresponse to a high electric field, such as immediately prior to alightning strike.

BACKGROUND

Lightning strikes are desirable to protect against, including withrespect to aircraft. One method of warning of an imminent lightningstrike includes measuring the strength of an electric field.

One approach in the prior art has included using electric field millswhich include a spinning set of fan blades that alternately cover anduncover an anode plate that is alternately charged by the electric fieldwhen uncovered and the charge state determined followed by discharge ofthe anode plate when covered.

While an electric field mill gives a good absolute measure of anelectric field, an electric field mill includes moving parts, such as ahigh rpm motor (e.g., 1650 rpm) and two metallic coaxial disks separatedby a fixed distance, and therefore has the drawbacks of being bulky,complex, and sensitive to stress and wear, requiring frequent servicing.

Accordingly there is a need for an electric field sensor that overcomesat least some of the drawbacks of prior art field sensors e.g., issmaller, has few or no moving parts, and requires less or infrequentservicing.

SUMMARY

An electric field sensor (whistle) is provided that may be used to warnof an imminent lightning strike. Some action may then be taken inresponse. The electric field sensor may be included on an aircraft.

In one exemplary embodiment, an electric field sensor is providedincluding an elongated conductor; a circuit including an input and anoutput connected across the elongated conductor wherein the circuitincludes a DC to AC signal converter; wherein the elongated conductor isoperative to impose a DC signal on the circuit input in response tobeing exposed to an electric field and broadcast an AC signal convertedfrom the DC signal in response to the electric field being greater thana threshold level.

In another exemplary embodiment, a lightning strike warning system isprovided including one or more electric field sensors mounted on orwithin a skin of a vehicle, the electric field sensors each including:an elongated conductor; a circuit including an input and an outputconnected across the elongated conductor wherein the circuit includes aDC to AC signal converter; wherein the elongated conductor is operativeto impose a DC signal on the circuit input in response to being exposedto an electric field and broadcast a radio signal converted from the DCsignal in response to the electric field being greater than a thresholdlevel; and, one or more radio signal receivers on the vehicle adapted toreceive the radio signal from the one or more electric field sensors.

In another exemplary embodiment, a method of sensing and warning of anelectric field is provided, the method including providing an elongatedconductor; providing a circuit including an input and an outputconnected across the elongated conductor wherein the circuit includes aDC to AC signal converter; generating a DC signal in response toexposure of the elongated conductor to an electric field; and,broadcasting an AC signal converted from the DC signal in response tothe electric field being greater than a threshold level.

In another exemplary embodiment, a method of warning of a lightningstrike near a vehicle in provided, the method including providing one ormore electric field sensors mounted on or within a vehicle skin, theelectric field sensors each including: an elongated conductor; a circuitincluding an input and an output connected across the elongatedconductor wherein the circuit includes a DC to AC signal converter;wherein the elongated conductor is operative to impose a DC signal onthe input in response to being exposed to an electric field andbroadcast a radio signal converted from the DC signal in response to theelectric field being greater than a threshold level; and, providing oneor more radio signal receivers on the vehicle, the one or more radiosignal receivers receiving the radio signal from the one or moreelectric field sensors.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

Exemplary embodiments of the invention will become more fully understoodfrom the detailed description and the accompanying drawings, wherein:

FIG. 1A is a representative implementation of the electric field whistleaccording to an exemplary embodiment.

FIGS. 1B-1E show exemplary antenna shapes according to exemplaryembodiments.

FIG. 2A is a representative implementation of the electric field whistleaccording to an exemplary embodiment.

FIG. 2B is a representative implementation of the electric field whistleaccording to an exemplary embodiment.

FIG. 3 is a representative implementation of a plurality of electricfield whistles according to an exemplary embodiment.

FIG. 4 is a representative implementation of a method of using theelectric field whistle according to an exemplary embodiment.

FIG. 5 is a representative implementation of an aircraft using theelectric field whistle according to an exemplary embodiment.

DETAILED DESCRIPTION

The following detailed description is merely exemplary (illustrative) innature and is not intended to limit the described embodiments or theapplication and the uses of the described embodiments. Furthermore,there is no intention to be bound by any expressed or implied theorypresented in the disclosure.

Referring to FIG. 1A is shown an exemplary embodiment of an electricfield whistle (electric field sensor) generally indicated by referencenumeral 10. The electric field sensor includes an antenna 14 and acircuit 20 connected in series where an output of the antenna 14 isconnected to an input of the circuit 20 and an output of the circuit 20is connected to an input of the antenna 14. In an exemplary embodiment,the antenna 14 may include a predetermined length of an elongatedconductor, such as a rod or square shaped length of metal e.g., of metalwire, or where the conductor is cylindrical or hollow at the center.

It will be appreciated that the elongated conductor may be embedded in asheath of insulating material or that the elongated conductor may beconductor lines deposited onto a substrate, such as an insulatingsubstrate. The elongated conductor may include any width, but in anexemplary embodiment, has a width (or diameter) of about 0.5 mm to about10 mm.

The antenna 14 between two antenna ends 14A and 14B need not bestraight. For example, the antenna 14 is preferably substantiallystraight as shown (e.g., rod or cylinder shaped) but it will beappreciated that the antenna 14 may include other geometrical shapes,such as wave shaped (e.g., FIG. 1B), coil shaped (e.g., FIGS. 1C, 1E),and arc shaped (e.g., FIG. 1D). It will be further be appreciated thatthe length of the antenna 14 will at least in part determine thefrequency at which a radio frequency signal is emitted (whistles) fromthe antenna.

In one exemplary embodiment, the antenna may have a length from about 1cm to about 50 cm, more preferably from about 10 cm to about 30 cm, andemits a signal (whistles) at a frequency that may range from about 140MHz to about 7 GHz, preferably from about 235 MHz to about 700 MHz.

Still referring to FIG. 1A, a circuit 20 is electrically connectedacross the antenna 14 (e.g., across each end of the antenna 14). A firstportion (e.g. first end) of the antenna 14A may be connected e.g.,wiring 15A to an input 22A of the circuit 20 where the input isconnected to a voltage dependent resistance device 22 which may be avaristor, zener diode or tranzorb (also referred to as Transzorb™) whichhas a high resistance at low voltage but rapidly loses resistance athigh voltage. Preferably, the voltage dependent resistance device 22includes a threshold voltage that an imposed voltage must be above inorder for electrical conduction to occur.

More preferably, the voltage dependent resistance device 22 may be atranzorb that conducts electricity in response to receiving a voltagesignal having a magnitude greater than the breakdown voltage of thetranzorb. For example, the tranzorb may clamp an output voltage to itsbreakdown voltage. In an exemplary embodiment, the voltage dependentresistance device 22 may have a threshold voltage of from about 15 to 50volts, more preferably from about 25 to about 35 volts.

The output from the voltage dependent resistance device 22 is output toDC to AC converter 24, which may be any conventional DC to AC converter.An output 24B from circuit 20 is then connected e.g., wiring 15B, to asecond portion (e.g. second end 14B) of the antenna 14. Preferably, anoutput AC (radio) signal frequency of the DC to AC converter may betuned (prior to use) to match the antenna, e.g., output a radio signalat or near the resonant frequency of the antenna, which may at least inpart be determined by the length of the antenna 14. The antenna, in turnemits (broadcasts) the radio signal (whistles) at or near the frequencyoutput by the DC to AC converter. It will be appreciated that theamplitude of the emitted radio frequency may be proportional to amagnitude of the sensed electric field (e.g., voltage at input of thecircuit 20). It will further be appreciated that the antenna 14 providesthe power source for the electric field whistle by virtue of itspresence in a changing electric field. The antenna 14 together withcircuit 20 makes up the electric field whistle (sensor) 10 according toan exemplary embodiment.

In exemplary operation of the electric field whistle, the antenna 14senses an electric field present over the length of the antenna, such asin the presence of an electric field surrounding a vehicle (e.g.aircraft 94) such as immediately preceding a lightning strike (St.Elmo's fire). The presence of the electric field causes a DC voltage tobe generated and input to the circuit 20 including tranzorb 22 whichonly allows a signal to pass to the DC to AC converter 24 if the voltageis above a predetermined threshold value. If the DC voltage is above thethreshold value, the DC to AC converter 24 then outputs an AC radiofrequency signal to the antenna 14 at a frequency matching the antenna14, which then whistles by broadcasting a radio frequency signal. Theradio signal may then be received by a radio receiver e.g., 30, whichmay be included in some other part of the aircraft 94 such as includedin electrical systems of the aircraft, e.g., 104, shown in FIG. 5, or bysome other radio receiver.

In response, a controller e.g., 32 may send a signal shutting downselected electrical system 34 in the aircraft, or issue commands causingother aircraft systems to take other action including at least one ofprior to, during or following sensing of the high electric field. Itwill also be appreciated that individual aircraft systems may include aradio receiver/controller capability programmed to respond without thenecessity of a separate receiver 30 and controller 32.

In exemplary operation, the electric field whistle is preferably able torespond e.g., sense an electric field circuit and send a radio signal onthe time scale of the order of milliseconds or less, allowing a warningto be received on the aircraft within from about 1 millisecond to about2 seconds prior to a lightning strike.

Referring to FIG. 2A, in an exemplary embodiment, the antenna 14 and/orassociated circuit 20 may be embedded within an aircraft skin 200, whichmay include a polymer composite material such as carbon fiber reinforcedpolymer. For example, the antenna 14 may be made about flush with thesurface of the aircraft skin to optimize sensitivity to an electricfield outside the aircraft, e.g., such as a high electric field (St.Elmo's Fire) present immediately prior to a lightning strike. It will beappreciated that the antenna 14 and/or associated circuit 20 may bemounted on a separate substrate, which may in turn be mounted on orembedded within the aircraft skin.

In another exemplary embodiment, Referring to FIG. 2B, the electricfield whistle may have the antenna 14 and associated circuit 20 arrangedsuch that the antenna 14 protrudes outward with respect to the aircraftskin 200, e.g., makes an angle theta θ of 90 degrees or less withrespect to the surface of the aircraft skin. For example, the antennamay include wiring to a protruding end by including a sheath conductorinsulated from the antenna 14 as wiring, similar to coaxial cable, wherethe core conductor is the antenna.

In another exemplary embodiment, referring to FIG. 3, the aircraft mayinclude a plurality of electric field whistles e.g., 31A, 31B, 31C, 31Din different parts of the aircraft 94 that are in radio communication(via whistling RF shown by arrows) with a receiver/controller 33 thatmay be programmed to predict a particular location e.g., 35 where alightning strike may occur with respect to the aircraft.

For example, by comparing the relative amplitudes of a plurality ofelectric field whistles, each of which emit an RF signal at a differentfrequency (e.g., have a different length) in response to a sensedelectric field, and where the amplitude of the emitted RF signals areproportional to the magnitude of the sensed electric field,receiver/controller 33 may be programmed to determine properties of theelectric field e.g., where the electric field is most intense, andthereby predict a location where lightning strike is most likely. Inresponse to a predicted location of a lightning strike, e.g., 35, actionmay then be taken by receiver/controller 33, such as shutting downsensitive electrical systems e.g., 37 in a particular area of anaircraft proximate to the predicted location of a lightning strike.

Referring to FIG. 4, is shown an exemplary method of operation of theelectric field sensors. In step 401, one or more electric field whistlesare provided near the surface of an aircraft skin. In step 403, the oneor more electric field whistles are exposed to a high electric field,such as that present from an imminent lightning strike, and generate anelectric field in response. In step 405, in response, each of the one ormore electric field whistles emits (whistles at) a respective RF signal.In step 407, in response, one or more RF signal receivers on theaircraft receive the RF signal. In step 409, in response, action istaken in at least one of before, during, and following a lightningstrike.

As shown in FIG. 5, the aircraft 94 may include an airframe 98 with aplurality of systems 96 and an interior 100. Examples of high-levelsystems 96 include one or more of a propulsion system 102, an electricalsystem 104, a hydraulic system 106, and an environmental system 108. Anynumber of other systems may be included. Although an aerospace exampleis shown, the principles of the invention may be applied to otherindustries, such as the automotive industry.

Although the embodiments of this disclosure have been described withrespect to certain exemplary embodiments, it is to be understood thatthe specific embodiments are for purposes of illustration and notlimitation, as other variations will occur to those of skill in the art.

1. A lightning strike warning system comprising: one or more electric field sensors mounted on or within a skin of a vehicle, said electric field sensors each comprising: an elongated conductor; a circuit comprising an input and an output connected across the elongated conductor wherein said circuit comprises a DC to AC signal converter; wherein said elongated conductor is operative to impose a DC signal on said circuit input in response to being exposed to an electric field and broadcast a radio signal converted from said DC signal in response to said electric field being greater than a threshold level; and, one or more radio signal receivers on said vehicle adapted to receive said radio signal from said one or more electric field sensors.
 2. The lightning strike warning system of claim 1, further comprising a controller in communication with said one or more radio signal receivers, said controller adapted to control one or more vehicle systems in response to said receiver receiving said radio signal.
 3. The lightning strike warning system of claim 1, wherein said one or more electric field sensors comprises a plurality of electric field sensors, each electric field sensor adapted to broadcast said radio signal at a different frequency.
 4. The lightning strike warning system of claim 3, further comprising a controller in communication with said one or more radio signal receivers, said controller adapted to predict a location of a lightning strike based on radio signals broadcast from said one or more electric field sensors.
 5. The lightning strike warning system of claim 4, wherein said controller is further adapted to control one or more vehicle systems in response to said predicted location of said lightning strike.
 6. The lightning strike warning system of claim 1, wherein said vehicle is an aircraft.
 7. A method of warning of a lightning strike near a vehicle comprising: providing one or more electric field sensors mounted on or within a vehicle skin, said electric field sensors each comprising: an elongated conductor; a circuit comprising an input and an output connected across the elongated conductor wherein said circuit comprises a DC to AC signal converter; wherein said elongated conductor is operative to impose a DC signal on said input in response to being exposed to an electric field and broadcast a radio signal converted from said DC signal in response to said electric field being greater than a threshold level; and, providing one or more radio signal receivers on said vehicle, said one or more radio signal receivers receiving said radio signal from said one or more electric field sensors.
 8. The method of claim 7, further comprising controlling one or more vehicle systems in response to said receiver receiving said radio signal.
 9. The method of claim 8, further comprising predicting a location of a lightning strike based on radio signals broadcast from said one or more electric field sensors.
 10. The method of claim 9, further comprising controlling one or more vehicle systems in response to said predicted location of said lightning strike.
 11. The method of claim 7, wherein said one or more electric field sensors comprises a plurality of electric field sensors, each electric field sensor broadcasting said radio signal at a different frequency.
 12. The method of claim 7, wherein said vehicle is an aircraft. 